1. Field of the Invention
This invention relates generally to industrial biological methods and processes for treatment of wastewater, wastewater sludges, and solid, liquid and gaseous organic materials, and is more particularly related to a counterflow system wherein the influent flows generally in a first direction and the sludge flows generally in the opposite direction.
2. Description of the Prior Art
Many biological technologies have been first applied to wastewater treatment, and later used in other applications, sometimes related to the environmental technologies. Wastewater treatment methods and apparatuses are described in literature, for example, in the following sources:
Water and Wastewater Engineering, Vols. 1 and 2 by Gordon Maskew Fair, John Charles Geyer and Daniel Alexander Okun, John Wiley & Sons, 1958; PA0 Biological Waste Treatment by Wesley W. Eckenfelder and Donald J. O'Connor, Pergamon Press, 1961; PA0 Water Preparation for Industrial and Public Water Supplies by A. A. Kastalsky and D. M. Mints, Publishing House Higher Education, Moscow, 1962 (Russian); PA0 Treatment of Natural Waters by V. A. Klyachko and I. E. Apeltsin, Publishing House Stroyizdat, Moscow, 1971 (Russian); PA0 Pysicochemical Processes By Walter J. Weber, Wiley-Interscience, New York, 1971; PA0 "Anaerobic Waste Treatment Fundamentals" by Perry L. McCarty, Public Works, pp. 107-112, September 1974, pp. 123-126, October 1974, pp. 91-94, November 1974, pp. 95-99, December 1974; PA0 Biochemical Treatment of Wastewater from the Organic Chemicals Manufacturing by F. V. Porutsky, Moscow, Publisying House Khimiya, 1975 (Russian); PA0 Chemistry for Environmental Engineering by Clair N. Sawyer and Perry L. McCarty, McGraw-Hill, 1978; PA0 Metcalf & Eddy's Wastewater Engineering Vols. 1 and 2, Edited by George Tchobanoglous, McGraw-Hill, 1979; PA0 Biological Process Design by Larry D. Benefield and Clifford W. Randall, Prentice Hall, 1980; PA0 Water Chemistry by Vernon L. Snoeyink and David Jenkins, John Wiley & Sons, 1980, PA0 Low-Maintenance, Mechanically Simple Wastewater Treatment Systems by Linvil G. Rich, McGraw-Hill Book Company, 1980; PA0 Biochemical Processes In Wastewater Treatment by S. V. Yakovlev and T. A. Karyukhina, Stroyizdat, Moscow, 1980 (Russian); PA0 Handbook on Design of Wastewater Treatment Systems, Edited by V. N. Samokhin and Boris M. Khudenko, Allerton Press, New York, 1986; PA0 Industrial Water and Wastewater Systems by S. V. Yakovlev, Ya. A. Karelin, Yu. M. Laskov, Yu. V. Voronov, Publishing House Stroyizday, Moscow, 1990 (Russian); PA0 Design of Anaerobic Processes for the Treatment of Industrial and Municipal Wastes, Edited by Joseph F. Malina and Frederick G. Pohland, Technomic Publishing Co., 1992.
Various fundamental and practical aspects of the relevant water and wastewater treatment processes are described in the above listed sources. These data are also applicable to other processes, for example, conversion of slid and liquid waste and other materials into biogas and biological fertilizers and soil augmentation substances.
Several modifications of wastewater treatment processes have been developed: 1. aerobic (activated sludge process, lagoon systems, and biofiltration), 2. anaerobic (various attached and suspended growth processes), and 3. combined anaerobic-aerobic systems.
Modern activated sludge systems are used for removal of organics and suspended solids, and for control of nutrients. In these systems, the predominant co-current flow of biomass (activated sludge) is used. In suspended growth systems, sludge recycle from the final sludge separator to the head of the treatment process is provided. These systems often incorporate several functional zones, usually called anaerobic (nonaerated, preferably with low nitrate and nitrite in the feed), anoxic (nonaerated, nitrite and nitrate present in the feed water) and aerobic (aerated, dissolved oxygen present in the water, nitrification occurs). Mixed liquor is recycled from downstream zones to upstream zones and the separated activated sludge is recycled from the final clarifier to the head of the process. A so-called single sludge is cultivated in all these zones. This is predominantly aerobic sludge. It includes very few strictly anaerobic organisms. Facultative anaerobic organisms develop in the nonaerated zone; therefore, the nonaerated zone in these systems should be more properly called the facultative zone. This term will be used in the application. The sludge recycle from the final clarifier is intended mainly for controlling the average sludge age, or average for the system food to microorganism (F/M) ratio. The upstream facultative zone serves to control the filamentous growth (selector zone) and to release phosphorus for its improved uptake in the aerobic zone. The facultatively anaerobic organisms are circulated with the sludge throughout the system. Anoxic zones are used for denitrification: the biological reduction of nitrites and nitrates formed in the aerobic zone and directed to the anoxic zone with the mixed liquor. These systems are used for treatment of municipal and low to moderately strong industrial wastewater. Examples of these systems are described in U.S. Pat. No. 3,964,998 and No. 4,876,883. The disadvantages of such systems including the following:
single predominantly aerobic sludge is formed in the system, such sludge having a poor diversity of species and a narrow range of oxidation-reduction and biodegradation ability; PA1 process can be used only for dilute to moderately strong wastewater; PA1 sludge concentration along the process train and along major process zones is almost uniform; PA1 F/M ratio in various process zones varies drastically; PA1 in the downstream sections, the wastewater concentrations are low, while the sludge concentration is about the same as upstream; accordingly, sludge dies off from lack of food, releasing nitrogen, phosphorus, and organics back into the water; PA1 sludge generation by mass and volume is high, accordingly, the sludge disposal costs are high; PA1 sludge age (10 to 30 days in the USA practice) is high and so is the corresponding degree of sludge stabilization; PA1 at high sludge stabilization, the content of organics anaerobically convertible to methane is low and so is the sludge mass and volume reduction in this conversion; PA1 degradation of soluble organic is poor due to limited oxidation-reduction potential (OPR) range, especially, xenobiotic, recalcitrant, or poorly degradable organics (halogenated, and others), PA1 usually, the SS content in the influent to the ASP process is limited by about 100 mg/l, otherwise removal of suspended solids is poor; PA1 process stability in response to dynamic overloading and toxic shocks is low; PA1 volatile organics may be emitted to the air in facultative, anoxic and aeration sections. PA1 almost uniform sludge make-up and concentration along the major process zones (poor F/M ratios in various process zones), and poor diversity of species in the sludge in each functional section; PA1 operational difficulties in treating low concentration wastewater; PA1 high sludge age and high degree of sludge stabilization in the aerobic subsystem (low content of organics convertible to methane and low mass and volume reduction in such conversion); PA1 poor removal of suspended solids; PA1 low process stability in response to dynamic overloading and toxic shocks; PA1 low efficiency of degradation of poorly and slowly degradable and toxic organics; PA1 loss of volatile organics to the air in open anaerobic, facultative, anoxic, and aeration sections; PA1 difficulties in removing nutrients (nitrogen and phosphorous).
The combined anaerobic-aerobic systems have been developed and used during the past fifty years for treatment of concentrated industrial wastewater. These systems incorporate a separate anaerobic subsystem (functional section) with the final anaerobic clarifier and sludge recycle, and aerobic subsystem (functional section) with the final clarifier as a sludge separation and sludge recycle step. Only excess aerobic sludge may sometimes be transferred to the anaerobic subsystem. This system has important advantages as compared to aerobic systems: high concentration waste can be treated, lesser quantities of sludge are produced, better removal of soluble and suspended solid organics can be achieved.
However, anaerobic and aerobic functional sections in the anaerobic-aerobic systems are only mechanistically coupled. Sludges in these sections do not interact: their make-up and properties abruptly change from anaerobic to aerobic stage. The major disadvantages of anaerobic-aerobic systems are as follows:
Several modifications of biofiltration systems have been developed, including aerobic and anaerobic, with and without recirculation, a single, or multiple-stage systems. Various lagoon system have also been developed. Most often they are a series of aerated or nonaerated sections. Hydraulic retention time in lagoons is very long and sludge recycle is not practiced. Processes in lagoons are usually similar to those in ASP, but not intensive and less controlled. Some lagoons may have an anaerobic section, often followed with aerobic sections. Such lagoons are similar to the anaerobic-aerobic systems. Large water volume in the systems insures equalization of wastewater and sludge concentrations and provides a substantial process stability. These systems are mechanically simple and require low maintenance. Many disadvantages of ASP and anaerobic-aerobic processes listed above are also typical for biofilters, lagoon systems and various other modifications of biological wastewater treatment.
Industrial biological methods, such as treatment of polluted gases, composting of solid waste, soil and waters bioremediation methods, treatment of fossil fuels (gas, oil, or coal) have many features in common with the wastewater treatment systems. They also have advantages and disadvantages such as those listed above.